The present invention relates to a forming apparatus for the production of a stranded conductor.
Heretofore, stranded conductors have been produced through the following three steps--drawing of coarse wire, annealing and stranding. Consequently, each step has required a large-sized equipment, that is, a large installation space and a large amount of power have been required. Having made extensive studies about the streamlined operations of such conventional stranded conductor manufacturing steps and about the method and equipment for producing a stranded conductor in a single step from the coarse wire drawing, the applicant of the present invention proposed various manufacturing methods and equipment, some of which have already been disclosed in Japanese Patent Application Laid-Open Publication Nos. 154590/81, 1533/82 and 165215/83 and Japanese Patent Application No. 64610/83. For example, in the forming apparatus filed as Japanese Pat. Appln. Laid-open Pub. No. 165215/83 as shown as a partially cut-away perspective view in FIG. 1, wire stock (not shown) fed continuous from a stock inlet 4' of a stock feed guide 4 such as a fixed shoe or the like provided on one side of a stock passage 3 which is formed between an inner rotating body 1 and an outer rotating body 2, both rotating bodies being adapted to rotate coaxially with each other, advances in the form of a coil through the stock passage 3. Before reaching the surface of a rotary head 5 disposed on the other side of the stock passage 3, said wire stock undergoes a compressive stress due to friction induced by the rotating bodies 1 and 2 and action of projections 6 or the like erected circularly on the surface of the rotary head 5 to be thereby heated and undergo a plastic deformation and is formed in the shape of a cylinder. Said cylinder is cut by cutting tools 7 and pushed out in the form of wires through wire passages 8 formed in the rotary head 5. Then the wires are stranded by virtue of rotation of the rotary head 5. In this case, the inner rotating body 1 which is rotated by a shaft 9 and the rotary head 5 which is rotated by a shaft 10, rotate at different speeds, and this difference in rotational speed permits the cutting tool 7 to effect cutting and forming.
FIG. 2 is an enlarged perspective view of the surface of the rotary head 5 shown in FIG. 1, in which the stock which has been cut by a cutting edge 7' of the cutting tool 7 is pushed into the wire passage 8 formed in the rotary head.
In the conventional forming equipment shown in FIGS. 1 and 2, however, the projections 6 erected on an end face 5' of the rotary head 5 are existent on only the outer rotating body side of the stock passage 3. So when the stock which advances toward the rotary head 5 in the form of a coil through the stock passage 3 is formed into a cylinder by compression, it is compressed from the outer rotating body side to the inner rotating body side by the action of the projections 6, thereby causing an excessive friction force on the wall surface of the inner rotating body 1 to the extent that the formation of a cylinder is not effected satisfactorily, with the result that the wire workability and strength may be deteriorated. Further, in the case of using the cut-forming die of FIG. 3 in place of the cutting tool, the diameter of the cutting edge 11 is relatively small as compared with the die body and is too small as compared with the thickness of the cylinder of the stock, therefore, the cutting efficiency of the die for the stock is deteriorated to a large extent. And in the case of a die having the cutting edge 11 of a diameter corresponding to the edge width of the cutting tool, the die body becomes large-sized and it is substantially impossible to attach the die body to the end face 5' of the rotary head 5.